The principal objective of this project is to reduce the mortality and morbidity of primary malignant melanoma of the skin of man. This objective has been achieved through the establishment of a Malignant Melanoma Clinical Cooperative Group (MMCCG). This group is comprised of four participating groups (Harvard, New York University, Temple and UCSF medical schools). During the two year feasibility study, the MMCCG will formulate and adopt a computerized, standardized protocol to be used in the study of patients with primary malignant melanoma of the skin. In addition, the MMCCG will develop a standardized approach to clinical and pathologic diagnosis of malignant melanoma which will lead to a TNM system and to clinical staging of melanomas. This standard approach to patients and their tumors will allow the evaluation of factors that indicate increased risk to acquire primary malignant melanoma of the skin (i.e. the population at risk) and factors that may indicate which persons with localized primary cutaneous malignant melanoma are at risk to undergo dissemination (e.g. variations in host immunity). A subsidiary aim of the MMCCG is the education of physicians, the allied medical professions, and patients in the recognition of pre-invasive primary malignant melanoma of the skin. This approach to patients coupled with the education of physicians will result in a decreased mortality and morbidity of primary malignant melanoma.